1. Field of the Invention
This invention relates to ion exchange processes using ion exchange materials comprising activated regenerated cellulose.
2. Brief Description of the Prior Art
An ion-exchange material in general consists of an inert polymer into which are introduced ionizable chemical groups which are normally basic or acidic in nature and capable of binding anions or cations, respectively, by a process analogous to salt formation. Such bound ions may be exchanged for different ions when the chemical environment of the material is changed.
Ion-exchange materials based on cellulose have been prepared by combining a suitable compound containing an ionizable chemical group with natural or regenerated cellulose. The hitherto proposed materials are, however, costly because of their expensive preparations and have other disadvantages.
A particular disadvantage of the hitherto proposed ion exchange materials based on natural or regenerated cellulose is their limited exchange capacity for relatively large ions, for example, ions derived from proteins or carbohydrates. Further, the previously proposed materials based on regenerated cellulose can be prepared satisfactorily in only a few physical forms. Thus, for example, difficulties arise in preparing an ion exchange material from cellulose that has been regenerated in the form of a sponge. The activating conditions tend to bring about a degradation of the sponge structure and produce a material in which the ion exchange active sites are irregularly distributed, and which as a tendency towards physical instability. Also, combination between the activating substance and the regenerated cellulose is mainly restricted to surface regions of the cellulose. Similar difficulties arise in activating cellulose that has been regenerated in other physical forms, for example, films.
The fibrous character of natural cellulose also imposes physical limitations, and restricts the range of applications for which ion exchange materials based thereon can be employed and renders such material unsuitable, for example, for the extraction of proteins from waste effluents.